One of the most active areas of work during the past five years in biochemistry and developmental biology has been the attempt to elucidate those factors involved in cellular development and differentiation in normal and abnormal cells. A great deal of speculation has been given to the role of tRNA in these processes. However, no cause and effect relationship has been shown. We have shown a direct relationship between altered tRNA and altered regulation of the isoleucine-valine and leucine enzymes in S. typhimurium. We plan to extend these studies by investigating the molecular mechanism by which tRNA participates in these regulatory systems by developing systems for making and detecting ilv specific m-RNA and proteins.